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General classes for dealing with social choice theory.

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package io.github.oliviercailloux.j_voting.preferences.classes;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import com.google.common.graph.Graph;
import com.google.common.graph.Graphs;
import com.google.common.graph.ImmutableGraph;

import io.github.oliviercailloux.j_voting.Alternative;
import io.github.oliviercailloux.j_voting.Voter;
import io.github.oliviercailloux.j_voting.preferences.ImmutablePreference;
import io.github.oliviercailloux.j_voting.preferences.Preference;

public class ImmutablePreferenceImpl implements ImmutablePreference {

	private ImmutableGraph graph;
	private ImmutableGraph graphIntransitivelyClosed;
	private ImmutableSet alternatives;
	private Voter voter;
	private static final Logger LOGGER = LoggerFactory.getLogger(ImmutablePreferenceImpl.class.getName());

	/**
	 * 
	 * @param voter  not null 
	 * @param graph  not null  graph with ordered Alternatives
	 * @return new ImmutablePreference
	 */
	public static ImmutablePreference asImmutablePreference(Voter voter, Graph graph) {
		Preconditions.checkNotNull(voter);
		Preconditions.checkNotNull(graph);
		return new ImmutablePreferenceImpl(voter, graph);
	}

	/**
	 * Transform Preference to ImmutablePreference
	 * 
	 * @param preference  not null 
	 * @return ImmutablePreference
	 */
	public static ImmutablePreference copyOf(Preference preference) {
		Preconditions.checkNotNull(preference);
		return new ImmutablePreferenceImpl(preference.getVoter(), preference.asGraph());
	}

	/**
	 * 
	 * @param voter  not null 
	 * @param graph  not null  graph with ordered Alternatives
	 */
	protected ImmutablePreferenceImpl(Voter voter, Graph graph) {
		LOGGER.debug("ImmutablePreferenceImpl constructor from graph");
		this.graphIntransitivelyClosed = ImmutableGraph.copyOf(graph);
		this.graph = ImmutableGraph.copyOf(Graphs.transitiveClosure(this.graphIntransitivelyClosed));
		this.alternatives = ImmutableSet.copyOf(graph.nodes());
		this.voter = voter;
	}

	@Override
	public ImmutableGraph asGraph() {
		return this.graph;
	}

	public ImmutableGraph asIntransitiveGraph() {
		return this.graphIntransitivelyClosed;
	}

	@Override
	public ImmutableSet getAlternatives() {
		return this.alternatives;
	}

	@Override
	public Voter getVoter() {
		return this.voter;
	}
}